The present invention relates to a finger joint cutter, which is a rotating cutting tool for processing finger joints, a kind of joint used with wood materials or the like.
As illustrated in FIG. 5, a finger joint cutter 1 includes a plurality of cutting portions 3 of a chevron wedge-like shape that project outward in a radial direction from a plurality of portions around an outer periphery of a body 2. A wedge-like finger joint F including a plurality of narrow and deep grooves at an end portion of an object M is cut using the cutting portions 3. Since such deep grooves are processed, the degree of wear of cutting edges of the cutting portions 3 of the finger joint cutter 1 will remarkably vary depending on regions of the cutting edges. The wear of cutting edges near the tip ends of the cutting portions that cut the groove bottoms of finger joints will be particularly large. Where the progress of wear of cutting edges near the tip ends of the cutting portions is fast, the progress of wear of the cutting edges at portions on a base side that continue into the worn tip ends of the cutting edges will become fast, and the life of the cutting portions will become short. For restricting such wear of cutting edges, it is possible to employ materials of high hardness such as high-speed tool steel or cemented carbide as a cutting portion material.
However, by forming the cutting edges of a high-hardness material, the toughness of the cutting portions will decrease which may lead to chipping of cutting portions. In particular, chipping of bases of cutting portions or peripheries thereof is apt to occur. Usage of the cutter will become almost impossible at the very point of time such chipping of cutting portions occurs. It will therefore become necessary to exchange replaceable blades or the cutter, and a drawback is presented in that the damage will be by far larger compared with simple wear of cutting edges. This is the reason why finger joint cutters having greater chipping resistance at the expense of lower wear resistance are generally employed. For instance, the hardness of the high-speed tool steel exhibiting wear resistance is adjusted through heat treatment to be relatively low, ranging around HRC 58 to 61.